1. Field of the Invention
The present invention relates to a moisture curable polyurethane composition comprising polyaldimine which forms polyamine by hydrolysis, and a water proof material, flooring material, sealing material, wall covering material and paint comprising the composition.
2. Description of the Prior Art
Polyurethane resin is excellent in various properties such as rubber elasticity, abrasion resistance and service life, and thus has particularly been used in recent years for paints, flooring material, water proof materials, adhesives, wall covering materials and sealing materials.
The polyurethane resin is substantially classified into two groups, that is, one component type and two component type. In the one component type, terminal isocyanate groups of a polyurethane prepolymer cure by reaction with atmospheric moisture after application to an object in site. In the two component type, a principal component containing polyurethane prepolymer and a curing agent containing polyols are mixed at the time of application in site to cause cure.
One component type polyurethane can be used by anybody because of its readiness in application method and has recently been attracted much attention in particular.
The one component type polyurethane is referred to as moisture curable polyurethane and following compositions have conventionally been known in the art.
(1) Moisture curable polyurethane compositions by using a reaction of polyisocyanate with moisture (water), that is, a reaction wherein a part of isocyanate is converted to amine by the decarboxylation of an isocyanate-water reaction product and resultant amine reacts with remainder of the polyisocyanate to progress curing. PA1 (2) Moisture curable polyurelthane compositions consisting of polyaldimine or polyketimine and polyisocyanate (British Patent 1064841 and German Patent 3607996A). PA1 (3) Moisture curable polyurethane compositions consisting of polyenamine and polyisocyanate (British Patent 1575666 and German Patent 2125247). PA1 (1) a moisture curable polyurethane composition comprising a polyaldimine represented by the formula (I): EQU Y--(N=CH-X).sub.n (I) PA1 wherein X is an aryl group having from 6 to 15 carbon atoms, Y is a divalent or trivalent hydrocarbon group having from 2 to 15 carbon atoms, or a divalent or trivalent polyoxyalkylene group having a molecular weight of from 70 to 6000, and n is an integer of 2 or 3; and a polyisocyanate and/or a polyurethane prepolymer having 2 or more isocyanate groups, PA1 (2) the moisture curable polyurethane composition wherein Y is an amino residue derived from a di- or tri-amine having a melting point of 50.degree. C. or less, PA1 (3) the moisture curable polyurethane composition wherein Y is an amino residue derived from an amine represented by the formula (II): EQU Z--(CH.sub.2 NH.sub.2).sub.n (II) PA1 wherein Z is a divalent or trivalent cyclo-, bicyclo- or tricyclo-aliphatic hydrocarbon group having from 6 to 13 carbon atoms, and n is an integer of 2 or 3, and PA1 (4) the moisture curable polyurethane composition wherein Y is an amino residue derived from isophorone diamine, 1,3-bis(aminomethyl)cyclohexane and 2,5- or 2,6-bis(aminomethyl)bicyclo[2,2,1]heptane. PA1 (5) a moisture curable polyurethane water proof material comprising the moisture curable polyurethane composition in one of the above (1) to (4) and a filler, PA1 (6) a moisture curable polyurethane flooring material comprising the moisture curable polyurethane composition in one of the above (1) to (4) and a filler, PA1 (7) a moisture curable polyurethane sealing material comprising the moisture curable polyurethane composition in one of the above (1) to (4) and a thixotropic agent, PA1 (8) a moisture curable polyurethane wall covering material comprising the moisture curable polyurethane composition in one of the above (1) to (4) and a thixotropic agent, and PA1 (9) a moisture curable polyurethane paint consisting of the moisture curable polyurethane composition in one of the above (1) to (4).
The compositions (1), however, have disadvantages of markedly poor curing ability and generation of bubbles in the application in site, though relatively good in storage stability in a sealed vessel. Amine or tin catalysts may be incorporated in order to improve curing ability. These additives, however, lowers storage stability of the compositions or accelerates bubble formation and is hence unsuitable for practical use.
In the compositions (2), polyaldimine or polyketimine reacts with polyisocyanate during storage. Consequently, in order to cure the compositions (2) by atmospheric moisture after application in site, it is required to inhibit the above reaction by providing steric hindrance for polyaldimine or plyketimine or by blocking isocyanate groups.
British Patent 1064841 and German Patent 3607996A have disclosed polyaldimines having steric hindrance in the molecules. These aldimines, however, are prepared from aliphatic aldehydes and are unsuitable for practical use because of slow curing rate and poor storage stability.
Polyaldimine disclosed in German Patent 3607996A, in particular, is prepared from aromatic amines and is excellent in various physical properties such as mechanical strength. However, the compound has an disadvantage that curing rate is slow and storage stability is poor at increased temperatures.
In the compositions (3), polyenamine also reacts with polyisocyanate. Consequently, when aromatic isocyanate is used as polyisocyanate, isocyanate groups must be blocked similarly to polyketimine and hence the compositions are also unsuitable for practical use similarly to polyketimine. On the other hand, it has been known that polyisocyanates having relatively low-reactivity, for example, aliphatic polyisocyanates or alicyclic polyisocyanates can be used for sealing materials in combination with polyenamine. The system has characteristics of non-bubbling and rapid cure.
However, polyenamine reacts, though very gradually, with aliphatic or alicyclic polyisocyanate and leads to poor storage stability in a long period or in somewhat increased temperatures, even though stored in a sealed containers. As a result, the sealing materials containing such polyenamine have a disadvantage that initial physical properties of the sealing materials cannot be retained or viscosity is remarkably increased and leads to very poor workability. Consequently, any of conventionally known prior arts has been unsatisfactory. That is, very important properties of these types of polyurethane are good storage stability in the sealed containers, excellent mechanical strength in the initial period of application, good retention of initial physical properties during storage at increased temperatures, prevention of gelation, good stability in viscosity, quick, curing by atmospheric moisture, and no bubble formation. The level of these properties determines commodity value of polyurethane products.
In other words, it is strongly desired to develop a moisture curable polyurethane composition which is excellent in storage stability in the sealed containers, i.e., capable of being stored under constant viscosity for a long period, rapidly curable without bubble formation in the presence of moisture, and outstanding in mechanical strength after curing.